Sunscreen containing UVA filter Mexoryl XL (upper part of the arm) provide significant protection against the induction of skin lesions in PLE patients. (Photograph courtesy of Andr Rougier, Ph.D.)

Asnires, France - The amount of ultraviolet A radiation (UVA) filtering is as important as labeled sun protection factor (SPF) levels in determining the effectiveness of sunscreens, according to Androugier, Ph.D. However the UVA blocker he prefers most, Mexoryl, remains unavailable in the United States as it awaits FDA approval.

"Much photodamage is produced by UVA rather than UVB. A good SPF is not enough. To be well protected you need a high SPF and a high UVA protecting factor at the same time. Moreover, the filtering system must be photostable, which is the case of only a few sunscreen products on the U.S. market," said Dr. Rougier, who is scientific director for La Roche-Posay Pharmaceutical Laboratories, Asnies, France, which is owned by L'Or,.

"In the States most of the products have deficient UVA filtering capacities," he continued. "The over-the-counter products are not sufficient compared with Europe and Asia in terms of UVA. In terms of UVB protection, it's OK. Mexoryl SX and Mexoryl XL [both patented by L'Or,] are two UVA filters that are used all over the world, but not in the States, and that is the best UVA protection. These filters have been approved in Europe, respectively, in 1992 and 1999, and in Japan in 1999 and 2002. Sunscreens containing these filters are available in Europe, Asia, Latin and South America. Millions of units have already been sold without any adverse effects."

Dr. Rougier and colleagues studied 20 women volunteers, average age 30, who were exposed to simulated UV radiation using a broad-spectrum UV lamp to induce photodermatosis. Each volunteer first applied sunscreens with SPF 60, but the topical agents varied in UVA protection measuring from 4 to 28, according to the persistent pigment darkening method (PPD). PPD is frequently used to measure UVA protection because its action spectrum extends across the UVA and is a biological end point rather than in vitro. Dermatologists observed each volunteer for the presence of polymorphous light eruption. Products with poor UVA protection also resulted in more significant skin damage.

Corroborating Research Professor Jean Krutmann and his research team at Heinrich-Heine University, Dusseldorf, Germany, also apparently support the use of Mexoryl as UVA protection agents. They followed 11 patients with photosensitive lupus erythematosus (LE). Each patient served as his or her own control, applying all three commercially available sunscreens in a double-blind comparative study. Using a standard phototest with a combination of UVA and UVB radiation, all patients developed LE-specific skin lesions. But the sunscreen with Mexoryl SX, Mexoryl XL, parsol 1789 and Ti02 to target against UVA rays "was by far the most effective in protecting 11of 11 patients." The other two sunscreens included parsol 1789 and Ti02 alone, protecting five patients with the second formulation and only three patients with the third formulation. The results were verified by strong ICAM-1 mRNA expression in unprotected test areas. The researchers concluded, "The use of sunscreens is beneficial to LE patients. Effective protection, however, might vary considerably between different sunscreens."

Dr. Rougier

A Canadian study shows SPF fails to provide enough information about how well sunscreens protect against UVA rays. University of Montreal, Quebec, researchers compared six sunscreens with SPF of 21 or more using the persistent pigmentation darkening method. After two hours, they found significant difference in UV radiation-induced pigmentation, confirmed by colorimetric and visual assessments. They concluded, "The labeled sun protection factor of the tested sunscreens was not predictive of the UVA protection level."

Studies by other investigators at the L'Oreal Research Center, Clichy, France, recommend people use daily protection against the sun. Twelve healthy volunteers were exposed five days a week to simulated solar radiation. The exposure time included one minimal erythema dose. They treated part of their skin with a daily use cream, containing UVA and UVB absorbers, including uvinul N539, parsol 1789, and Mexoryl SX.

After six weeks, the untreated skin showed signs of several biological changes, while the cream appeared to prevent them. The untreated skin had significant increases in stratum corneum and stratum granulosum thickness, increased tenascin expression but decreased type 1 procollagen in the dermis, as well as melanization and changes in skin hydration and microtopography.

Catching Up "When they prescribe sunscreens to patients, dermatologists should be aware both of the SPF and UVA protection ... that is the main issue," said Dr. Rougier. "Americans are probably the worst who are not protected from the sun and particularly from UVA radiations."

Sun exposure is well documented to cause skin photoaging and eventually, various forms of cancer. "The aim of sunscreens is not to increase sun exposures, but to decrease risks of reasonable exposures. Even well protected, sun is dangerous, Dr. Rougier said.

La Roche-Posay and LOral funded Dr. Rougier's research.